Arc lamp



H. R. BENSON Oct. 28, 1952 ARC LAMP 5 Sheets-Sheet 1 Filed March 3, 1950 INVENTOR. llarold 2. 38125011.

BY zadmu M nila/ 16% f Oct. 28, 1952 H. R. BENSON 2,616,059

ARC LAMP Filed March 3, 1950 5 Sheets-Sheet 2 IN VEN TOR.

.1 i .lfarold e. Bans-01L L 1 any;

lww iiu w w w H. R. BENSON Oct. 28, 1952 ARC LAMP 5 Sheets-Sheet 4 Filed March 3, 1950 INVENTOR. Harold R. Benson.

BY $1440 0, MW

Oct. 28, 1952 H. R. BENSON 2,616,059

ARC LAMP Filed March 3, 1950 5 Sheets-Sheet 5 IN VEN TOR.

Harold R. Benson Patented Oct. 28, 1952 ARC LAMP Harold R. Benson, Maywood, 111., assignor to NuArc Company, Chicago, 111., a corporation of Illinois Application March 3, 1950, Serial No. 147,560

17 Claims.

The present invention relates generally to are lamps and more particularly to an arc lamp especially adapted for use in the graphic arts industry where an accurately controlled light source of a constant predetermined intensity is desired, as in photographic departments and the like.

Are lamps have heretofore been extensively employed in the graphic arts industry since they provide a means for producing in an efficient manner a very intense source of illumination. Conventionally such lamps comprise carbon electrodes associated with a suitable reflector with means for controlling the feed of the carbon electrodes. It is desirable that such are lamps produce a definitely controlled light which is exactly the same each time it is used as far as the intensity and Kelvin temperature is concerned, so that definite standards for exposures in the graphic arts industry may be maintained. Heretoiore such are lamps have been unsatisfactory in that the light produced is not steady, and if with such prior lamps a plot of foot candles or Kelvin temperature versus time were made, a curve having considerable variation would be obtained. This is due to numerous factors. For example, it is well known that substantial variations in the voltage or" the source supplying the electrical energy for the arc lamp constantly occur. Also, the carbons employed are not absolutely uniform in that they have hard and soft spots which burn at different rates of speed. It would be desirable to provide an arc lamp with improved control means whereby the Kelvin temperature and foot candles output would remain substantially constant over long periods of time, thereby eliminating guess work with respect to exposure time in the graphic arts industry with the resul nt extensive reshooting heretofore necessary. It is furthermore desirable to provide a single source light for the graphic arts industry which assures clear and sharp line definition in connection with photographic work with improved automatic means for maintaining a constant light intensity regardless of the impurity of the carbon electrodes or the variations in line voltage. With such an arrangement long exposures resulting in fuzzy line definition will become a thing of the past and sharp, perfect exposures producing clear,

sharp line definition are the usual result. Obviously, any reduction in exposure time saves money since its cuts down the power consumption of the arc lamp and reduces the time which the operator must pend in waiting for exposures, to say nothing of retakes or reshooting which is-so commonly the case with prior art arrangements.

It is an object of the present invention to provide a new and improved arc lamp particularly well adapted for use in the graphic arts industry.

It is another object of the present inventionto provide an arc lamp with means for definitely and accurately controlling the light so that it has the same intensity at all times, independently of voltage variations or the like, thereby enabling definite standards of exposure to be established.

It is another object of the present invention to provide an arc lamp which is more economical, more efficient and produces more satisfactory light than prior art arrangements and which furthermore will give many years of foolproof service.

Still another object of the present invention resides in the provision of an improved arc lamp which requires but a fraction of the power employed in prior art devices, which enables the exposure time in the graphic arts industry to be greatly reduced and at the same time permits a remarkable step up in production.

It is a further object of the present invention to provide an improved arc lamp which is efiective at the flip of a switch to produce a high intensity light without flicker and without substantially any variation in intensity or color.

Still a further object of the present invention resides in the provision of an improved arc lamp with automatic control means for maintaining the are at a constant length regardless of the impuritie in the carbon electrodes, and regardless of line voltage variations.

Further objects and advantages of the present invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the present invention, reference may be had to the accompanying drawing in which:

Fig. v1 is a perspective view of an arc lamp embodying the present invention;

Fig. 2 is a schematic clrcuit diagram illustrating the electrical control and power circuits associated with the arc lamp of Fig. 1;

Fig. 3 is a vertical ectional view taken along line 3-3 of Fig. l with certain cover or housing portions removed;

Fig. 4 is a rear view looking in the direction of the arrows il3 of Fig. 1 with the mechanism cover removed, more clearly to illustrate certain details of the present invention;

} Fig. 5 is an enlarged detailed view, partly in section, of portions of the apparatus viewed from the same direction as in Fig. 4;

Fig. 6 is a sectional view taken on line 6-6 of Fig. 5;

Fig. 7 is a sectional view taken on line 1-! of Fig. 5 with certain parts of the apparatus shown in phantom;

Fig. 8 .is an enlarged sectional view of only a portion of the apparatus taken along line 8-8 of Fig. 4;

Fig. 9 is an enlarged view of a portion of the apparatus shown in Fig. 3;

Fig. 10 is a. side elevational view illustrating a modification of the present invention with respect to the carbon electrode supporting means; and

Fig. 11 is a sectional view taken on line llll of Fi 10.

In accordance with the present invention, there is disclosed an arc lamp which provides constant illumination under all conditions by maintaining a constant current flow through the are whether the voltage is high or low, and regardless of the impurities in the carbons forming the electrodes of the arc lamp. There is provided an improved striking means for causing striking of the are which insures straight line motion of the electrodes and an improved mechanism and control means for causing simultaneous movement of the carbons to insure an arc of the same illumination intensity at all times. Transformer means are included to provide a high are current with power factor correction means to provide a minimum power consumption. The carbons are fed automatically to maintain a uniform gap in response to a sensitive current relay which maintains a predetermined constant current flowing through the carbon electrodes. lay controls a motor feed for the carbons maintaining them the same distance apart regardless of the burning rate of the carbons, thereby insuring exactly the same light each time the lamp is used. With this arrangement it is immaterial whether the line voltage fluctuates, which it is wont to do.

Referring now to the drawings and particularly Fig. 1 thereof, ther is illustrated the improved arc lamp I of the present invention which comprises a suitable reflect-or ll specifically illustrated as having a rectangular cross section and being constructed in the form of a truncated pyramid. The are lamp in further includes a main supporting post i 2 to which the reflector I i and associated control mechanism, dis- .posed within a suitable .housing defined by a cover member I3, is mounted as described in greater detail hereinafter. The post I2 is supported on a three armed support comprising arms i illustrated as disposed in a horizontal plane with the ends of the arms supported on suitable casters H. An electrical power and control unit described in greater detail hereinafter is disposed within a suitable housing [8 supported on the arms i5, the post I2 extending up through the center of the housing I8 which latter is provided with a suitable cover 20. The housing i8 is provided with suitable louvres 2i whereby cooling air may circulate therethrough to prevent the power unit contained within the housing from reaching inordinately high temperatures. A suitable power cord 23 is connected to the means disposed within the housing l8 to supply the electrical units contained therein with electrical energy from a source not shown. Preferably the conductor 23 is adapted to be connected to an alternating current source having a potential of 220 volts, although it will be obvious from the ensuing description that the particular magnitude of voltage mentioned may vary over a wide range, and means are provided to take care of such voltage variations. A control cable 25 supplies the necessary current for the are as well as the control current for controlling means asso- This reciated with the electrodes designated by the ref-' erence numerals 21 and 28 in the drawings.

In order to obtain an overall picture of the electrical circuit of the arc lamp of the present invention and before discussing various details thereof, reference may be had .to Fig. 2 of the drawings where the electrical circuit of the arc lamp I0 is illustrated and which furthermore schematically discloses the more important elements of the device. The corresponding parts of Fig. 2 are designated by the same reference numerals as in the other figures of the drawings. As there illustrated, the power cord 23 is connected to a. suitable source of electrical energy designated by the reference numeral 28. A suitable control switch 29, also shown in Fig. l of the drawings. controls the application of power to the power control unit disposed within the nousing I8 which essentially comprises a transformor 30, control relays 3| and 32 and fine and coarse tap changing switches 33 and 3 1, respectively.

The transformer 31] comprises a tapped primary winding 36 and a secondary winding 31. The primary winding is provided with a plurality of taps designated by the reference numerals 33a, 38b, 38c, 38d, 38c, 38 385/, 38h, and 381'. The taps 38a and 381) are respectively connected to the taps 34a and 34b of the coarse adjustment tap changing switch 34, while the taps 38c, 3801, 38e, 38f, 38g and 38h are connected respectively to the taps 33c, 3311, 33c, 33 339 and 3312. of the fine adjustment tap changing switch 33. These tap changing arrangements are provided since it is desirable for the lamp to produce a, constant light intensity under any voltage conditions and it is, therefore, necessary to provide the primary transformer winding 36 with the suitable taps to accommodate the various voltages to which the unit might be connected. So that the proper settings of the tap changing switches 33 and 34 may be determined, there is provided a volt meter 40 connected across the power source 28. The power switch 29, the tap changing switches 33 and 34 and the'volt meter 40 are suitably mounted on .the cover 20 of the housing [8, as is clearly indicated in Fig. 1 of the drawings, to provide in a convenient place the control means for the arc lamp I0.

Although a particular voltage source such as 28 might nominally be termed a 220 volt source, it is well known that the voltage from such a 220 volt source might vary over a substantial range which, for example, might be the range of 200 to 252 volts. The tap 3 3a. of the tap changmg switch 34 is preferably for source voltages within the range of 200 to 225 volts so as to tend to raise the output at the secondary winding 31. The tap 34b of the tap changing switch 34 is primarily for voltages within the range of 225 to 52 volts. The tap changing switch 33 is capable of adjusting for small voltage increments within the two ranges of the tap changing switch 34 so that whether the voltage of thesource 28 be close to 200, close to 252 or exactly 220 volts, there will appear across the secondary winding 3'] of the transformer 30 a voltage which is always the same except for minor fluctuations of the voltage source.

The secondary winding 31 of the power transformer 30 is connected to the carbon electrodes 21 and 28 of the arc lamp l0 through power conductors 25a and 2522 contained in cable 25. In this high current circuit, which for a particular embodiment constructed in accordance with the present invention had a current flow of amperes, there are serially connected the windings 3| and 32 of the current relays 31 and 32, respectively. The relay 3| is a constant current control relay while the relay 32 is an arc strike relay, both described in greater detail hereinafter. The relay 3| is provided with movable contact members 3 la and 31b while the relay 32 is provided with normally open contacts 320.

For the purpose of maintaining constant the current flow through the carbon electrodes 21 and 28, which is a function of the arc gap between these electrodes, there is provided a reversible electric motor generally designated at 40 suitably connected by a driving mechanism, schematically indicated by dashed lines, with the respective electrodes 21 and 23 so that these electrodes are simultaneously moved either toward each other or away from each other, depending upon the particular direction of rotation of the motor Ml.

This motor t e is illustrated as of the conventional type of motor having windings 4| and 42, respectively, sometimes referred to as a quarter phase motor. The winding 42 is adapted to be connected by the conductors 25c and 25d included in cable 253, with the taps 34a and 34b of the tap changing switch 34 which in turn are connected to the power source 23 in series with a portion of the primary winding 35 or the transformer thereby to provide a control voltage of reduced potential. When the switch 29 is closed, the winding 42 is energized. However, rotation of the armature es of the motor 40 will not occur unless the winding 4! is also energized, and the direction of rotation will depend upon th relative polarities of the alternating potentials supplied to windings 41 and 42.

For the purpose of controlling the condition of energization of the winding 41, the current control relay 3] is provided with reversing switch contacts a and em for connecting the winding 4! to the power source with opposite connections depending upon the operating condition of the relay Bl. When the Winding 3| of the relay 3| is not energized, the switches 3 la and 3 lb engage contacts and 4513, respectively, so that if power is supplied to the winding 41 through the switch contacts em and 3519, the motor will rotate in a direction to move the electrodes 2'! and 28 toward each other to strike an arc therebetween. When an arc has been struck and current flows through the winding 3|, the relay 3! is energized, and if the current exceeds a predetermined value the contacts 34a and 3lb will engage with contacts 45a and 45?), respectively, to reverse the direction of rotation of the motor 40. The contacts 16a and 5512 are connected by the conductor 25 with one terminal of the winding 4|, while the other terminal is connected by the conductor 25g with the contacts 45a and 461). If the current now through th electrodes 21 and 28 is exactly right, the switch contacts 31a and '3lb will remain in some intermediate position and the rotor 43 or the motor 40 will remain stationary. As the carbon electrodes 21 and 28 are consumed, the arc length will tend to increase, and relay 3| will maintain constant the current flowing through the electrodes by causing motor 40 to move the electrodes 2'! and 28 toward each other thereby maintaining constant the intensity of the illumination produced.

The control circuit shown in Fig. 2 of the drawings includes in addition an arc strike control solenoid 53 having a movable armature 5! described in greater detail hereinafter. Specifically, the arc strike control solenoid is de- 6 signed when energized to instantaneously separate to the desired extent the carbon electrodes 21 and 28 to draw an arc therebetween. One terminal of this solenoid 58 is connected by means of the conductor 250 to the terminal 34a. and hence to one side of the alternating current source 28 through the switch 29. The other terminal of the winding of the solenoid 50 is connected by means of a conductor 25c and the contacts 32a of the strike control relay 32 to the terminal 34b and hence to the other side of the source of potential 28. When the switch 29 is closed and current flows through the carbon electrodes 21 and 28, as when these electrodes touch each other, the strike control'rela'y 32 is energized to close its contacts 3211, with the result that the solenoid 59 is energized to move the upper carbon electrode 21 out of contacting engagement with the lower carbon electrode 28 to draw an arc therebetween.

For the purpose of supporting the reflector H and the carbon electrode control mechanism from the post I2 there is provided a supporting frame 54 comprising two angle members 55 and 56 held in spaced parallel relationship by cross frame members 51, 58, 59 and 60, the cross frame members being welded to the angle members 55 and 58 to provide a sort of ladder construction. The angle frame members 55 and 5e are each provided with one flange of uniform width from top to bottom while the other flanges of each angle member designated respectively as 55a and 58a have a somewhat triangular configuration with a notched central portion designated respectively as 55b and 55b to receive therein a portion of the deflector l l as is clearly indicated in Figs; 1, '3 and '7 of the drawings. The frame cc is supportedfrom the post [2 on a horizontally disposed stud 69 which is threaded as indicated at 55a in Fig. 4 of the drawings into a head El fastened on a post 52 telescopically related with the post 12. The upper end of thepost I2 is provided with a clamping means 63 best shown in Figs. 1 and 4 of the drawings, including a manually actuable lever for clampingly relating the upper post 62 and the lower post I2 in any predetermined telescopic relationship whereby the vertical position of the reflector ll may be adjusted as desired. Preferably a suitable safety collar 6.! is clamped to the upper post 62 above the clamping member 63 to limit the downward movement of the frame 54 and associated members supported thereby when it is desired to rotate the post 62 about its longitudinal axis and consequently pivot the reflector ll about a vertical axis.

In order to permit pivoting of the frame 5t and consequently the reflector I! about a horizontal axis in a controlled manner, there are welded to the outside faces of the angle members 55 and 56 clutch elements H] and H, each constructed in the form of a cone-shaped washer having an annular frictional surface. These elements are welded so as to form an integral part of the frame member 54. The supporting bolt 60 passes through suitable openings defined 1n the frame member 54 and the elements "Hi and ll. The head BI is also provided with a cooperating annular surface 64a, and disposed between this face 61a and the annular surface of the element is a friction member it which may comprise a leather washer or the like. Similarly, cooperating with the annular surface of the element H is another annular friction member 15 which is disposed coaxially with the stud B0 and positioned between this member 15 and the element II is a washer I6 preferably identical with the member I4. A suitable nut Ill having a manually graspable lever portion 78 is associated with the end of the stud 60 not disposed in the head 6|. It will be apparent that by means of the nut 11, a clamping force will be applied tending to press the annular surfaces of the elements or member 6|, I0, II and "I into intimate frictional engagement with the interposed washers I4 and 15. By loosening the nut if, the frame 54 may be pivoted about a horizontal axis comprising the bolt or stud 60 and may be clamped in any desired angular position with reference to this horizontal axis. It should be understood that instead of smooth surfaces and frictional washers of leather or the like, that the surface 6Ia of the head may be provided with radial teethi or notches to engage with a corresponding surface on the element I9 to provide more positive clamping should this be desirable.

For the purpose of supporting the reflector II from the frame 54 there is provided a reflector support 89 in the form of a channel member of a size to be disposed between the angle members 55 and 59 in the manner best shown in Fig. 7 of the drawings. The flanges of the channel member 89 are preferably welded or otherwise secured to the flanges 55a and 56a respectively of the angle members 55 and 56. 89 is provided with suitable openings through the flanges thereof which are in alignment with the openings through the angle members 55 and 59 for accommodating the stud 69 defining the horizontal axis for the frame member 54. The reflector I I is suitably bolted to the reflector support 89 by bolts 82 best shown in Fig. 3 of the drawings which bolts extend through a porcelain plate 89 closing the small end of the truncated pyramid shaped reflector. These bolts are illustrated as extending through integral flanges No. of the reflector II, thence through a heat insulating plate 85 and finally through the reflector support 89. The heat insulating plate 95 greatly retards the transfer of heat from the reflector I i to the mechanism associated with the frame 59. The reflector II is preferably formed of metal and may have a suitable metal reflecting surface on the interior thereof. The plate 33, however, is subjected to spattering of arc particles and for this reason is preferably made of porcelain rather than metal.

The frame member 54 further includes a pair of narrow plates 99 and 88 which are arranged in spaced parallel relationship and at right angles to the cross frame members 59 and 59 as is best shown in Figs. 5 and 7 of the drawings. Preferably the plates 89 and 88 are welded to the cross frame members 59 and 59. It will be apparent that a groove extending in the direction of the frame members 55 and 56 is defined between the narrow plates 86 and 88. Disposed within this groove and extending along the frame member 59 in spaced parallel relationship are a pair of tubular members 99 and 9| each having a rectangular cross section as is clearly shown in Figs. 6 and '7 of the drawings. The central portions of the tubular members 99 and 9| are disposed within the groove defined between the members 96 and 8B. The upper and lower ends of these tubular members are suitably fastened to the cross frame members 5'! and 99, respectively, of the frame 54 as by fastening means 92. The adjacent faces of the tubular members 99 and 9| at the upper and lower,

The member 9 ends thereof are provided with elongated slots designated as a and 9Ia, respectively, at the upper ends thereof and 90b and 9Ib at the lower ends thereof for permitting reciprocal movement therein of an upper carbon carriage 93 and lower carbon carriage 94, respectively. The central portion of each tubular member 90 and 9| is notched in an arcuate manner as indicated at for the member 9| in Fig. 5 of the drawings for a purpose which will become apparent from the following description.

In order to cause reciprocal movement of the upper carbon carriage 93 within the slots 99a and 9m of the tubular members 99 and 9I, respectively, there is provided a rack 99 disposed within the tubular member 90 and having its upper end fastened as indicated at 99 to the upper carriage 93. Similarly, to support the lower carbon carriage 94 within the slots 9% and 9Ib of the tubular members 99 and 9!, respectively, there is provided the rack I99 disposed within the tubular member SI, and having its lower end fastened as indicated at IDI to the lower carriage 94. It will be apparent that if a suitable gear member I 92 centrally disposed with respect to the frame member 59 is caused to drivingly engage the racks 98 and I90, respectively, as indicated in Fig. 5 of the drawings, rotation of the gear I02 in either direction will cause simultaneous and opposite movement of the racks 99 and I00 in the direction of their longitudinal axes within the tubes 99 and 9I, respectively. It will now be apparent that the arcuate notches 95 are to permit the gear I02 drivingly to engage both the racks 98 and I90. Thus, for one direction of rotation of the gear I92, the carbon carriages 93 and 94 will move toward each other and for the other direction of rotation, will move apart. When the carriages 93 and 94 are brought close together, the upper end of the rack I 99 moves adjacent the carriage 93, while the lower end of the rack 98 moves adjacent to rack 94. Preferably the upper end of the rack I99 is provided with a longitudinally extending slot I09a and the lower end of the rack 98 is provided with a similar longitudinally extended slot 98a to receive therein the ends of the carriages 93 and 94, respectively. This construction permits the carriage 99 to extend for a substantial distance into the tube 9i without interfering with movement of rack I90, and similarly the carriage 94 I is permitted to extend for a substantial distance .into the tube 99 without interfering with movement of the rack I99. It will be obvious that this arrangement provides a much more satisfactory support of the carriages 93 and 94 to guide them in their movement and prevent lateral displacement thereof.

To control movement of the upper and lower carriages 93 and 94, respectively, there is provided a power assembly unit including the gear I02 best shown in Fig. 3 of the drawings and designated by the reference numeral I95. This power assembly unit includes the motor 99 and comprises a frame I96 of U-shaped configuration having the bight portion thereof suitably bolted or otherwise secured as by the fastening means I91 to the horizontal frame members 58 and 59, whereby the bight of the U-shaped frame member I96 clamps the tubular members 90 and 9| in position and tends to firmly support them at the central portion and maintain them in vertical alignment. As indicated, the

gear I02 is mounted on a horizontally disposed shaft I01 journalled in bearing members defined in frame members I09 and I I suitably welded to the legs and bight respectively of the U- shaped frame member I05. The gear member I02 is keyed to the shaft I01 as indicated at H2 in Fig. 8 of the drawings. The shaft I01 is furthermore provided with one or more flat surfaces at the end I01a thereof to receive a manually actuable knob III whereby the gear I02 may be manually rotated as desired. The motor 40 is also adapted to drive the gear I02 through a suitable reduction gear mechanism comprising a worm gear II3 mounted on the motor shaft which worm gear meshes with a gear H5 rotatable with a horizontally disposed shaft H5 forming part of the power unit I06. Also disposed on the shaft H5 is a small gear H3 drivingly engaged with a large gear II1 disposed on the shaft I01. The arrangement of these gears is such that a substantial speed reduction occurs between the shaft of the motor 40 and the shaft I01.

For the purpose of permitting manual rotation of the gear I02 without interfering with the operation of the motor 40, a suitable friction clutch is provided between the gear II 1 and the gear I02. As illustrated, a friction member II8 best shown in Fig. 8 of the drawings is disposed between the adjacent faces of the gears I02 and H1. In addition, a. friction plate II9 biases a friction washer I against the other face of the gear H1. The friction members H8 and I20 are biased into frictional engagement with the surfaces of the gears I I1 and I02 by virtue of a compression spring I2I clearly shown in Fig. 8 of the drawings. Under normal conditions rotation of the gear II'I will cause rotation of the gear I02 by virtue of the friction member II8 interposed therebetween. However, when the shaft I01 is manually rotated, slippage occurs between the gear H1 and the gear I02.

In order to support the lower carbon electrode 28 from the carriage 94, there is provided a suitable casting I which is fastened as by fastening means I20 to the carriage 94. This casting includes a carbon clamping portion I21 for clampingly engaging the lower carbon electrode 28 so as to support it in a vertical position for movement along a vertical axis. This clamping portion 121 is electrically insulated by suitable means not shown from the carriage 94 so that conductor 2517 may be electrically connected to clamping means I21. The reflector I I is provided with suitable openings IIb and Ho wherethrough the ends of the carbon electrodes may extend to permit the arc to be drawn within the reflector II. These openings are preferably large enough so that a portion of the carbon support, such, for example, as carbon clamping means I21, may also be received to permit utilization of the maximum amount of the carbons.

In order to support the upper carbon 21 from the upper carriage 93 there is provided, as best shown in Figs. 3 and 9 of the drawings, a suitable casting I30 which is bolted or otherwise secured to the upper carriage 93. This casting I30 includes an opening I3I defined therein for receiving a hollow insulating bushing I33 preferably formed of lava or other suitable material which is a satisfactory electrical insulator and at, the same time is capable of withstanding high teme peratures. The upper electrode 21 is adapted to be slidingly disposed within the central opening of the bushing I33.

As was mentioned above, the are striking solenoid 50 is capable of causing high speed separation of the carbons 21 and 28 in order to draw the are initially, and to this extent it is desirable for the carbons to contact each other when no current flows therethrough. It is for this reason that the upper carbon 21 is reciprocally movable in the lava bushing I33. To insure straight line motion of the carbon 21 during the movement produced by the solenoid 50, there is provided a straight line motion mechanism comprising a carbon lift plunger I34 reciprocally movable in a suitable recess defined in the casting I30 which recess has its longitudinal axis parallel with the axis of the carbon electrode 21. This lift plunger I34 is connected by a link I35 having a forked end I3'5a for engaging a head I30 suitably clamped as by clamping means I31 to the upper carbon 21. The link I35 is insulated from the carbon lift plunger I34 by means of suitable mica washers disposed above and below the link I35 where it is fastened to the plunger I35 and an insulating bushing surrounding the portion of the plunger I34 which preferably passes through a suitable opening in the link I35. The lift plunger I34 is provided with a head I40 which is bifurcated to receive therein a link I4I pivotally connected thereto by pin I42. This link in turn is pivotally connected to one end of a lever I40 which lever is pivotally connected as indicated at I41 to the casting I30. The other end of the lever I40 is connected by a short link I50 with the armature 5I of the solenoid 50. Energization of the solenoid 50 will cause the armature 5i to move downwardly as viewed in Fig. 3, of the drawings and hence will cause relative separation between the carbons 21 and 28. When the solenoid 50 is deenergized, as indicated in Fig. 3, then the upper carbon 21 is moved downwardly so as physically to engage the lower carbon 28. As soon as current flows through the carbon electrodes 21 and 28, the solenoid 50 is energized to cause separation of the electrodes 21 and 28 with the consequent production of an arc therebetween. The lower carbon 28 is so disposed that the arc is drawn at the center of the reflector II. In order to aid gravity in causing the electrodes 21 and 20 to move to the position shown in Fig. 3 when the solenoid 50 is deenergized, a suitable compression spring I5I is provided which tends to bias the armature 5I into the position indicated in Figs. 3 and 4 of the drawings. It will be understood that the armature 5I must also be supported from the carriage 93 and preferably the same bolts or fastening means for holding the casting I30 to the carriage 93 also hold the solenoid 50 in position with respect to this carriage.

For the purpose of electrically connecting the upper electrode 21 with the power source, there is provided an insulated lead I52 which is connected to the member I36 and to a terminal I53 suitably insulated as by means of an insulator I54 from the lever I46 at the pivot point I61. Power is supplied to this terminal which is relatively stationary in the manner shown in Fig. 2 of the drawings through the conductor 25a which is included in the cable 25.

Supported from the lower end of the frame 5 4 is a carbon drip pan I51 for receiving any are particles produced when are current flows between the electrodes 21 and 28. Preferably a suitable Allen wrench I60 is supported from a Chain or other flexible member attached to the frame. 54 which wrench is employed to control the clamping motion for the upper and lower carbon holders I21! and I3? when it is necessary to change the carbons.

In View of the detailed description included above, the operation of the present invention will readily be understood by those skilled in the art. The reflector I I is initially adjusted at the proper vertical height and at the proper angle, both horizontal and vertical, through suitable manipulation of the manually adjustable levers 65 and I3. It is assumed that the electrodes 2'! and 28 are normally in the position indicated in Fig. 3 of the drawings. Upon closing the switch 29, the volt meter 48 indicates the voltage of the source 28 and th tap changing switches 33 and 34 are adjusted for the proper range of voltage to assure a uniform arc temperature and consequently uniform illumination under all conditions. Upon closing of the switch 29 with the carbon electrodes 2'! and 28 in the position indicated in Fig. 3, current will iiow through the conductors 25a and 25b and consequently through the carbon electrodes 27! and 28. This current will also flow through the serially arranged windings 3i and 32' of the relays SI and 32, respectively. The latter will close its contacts 32a to energize the arc striking solenoid 58 which will separate the electrodes 21 and 28 to draw an arc therebetween, by moving the upper carbon 21 upwardly to the limit of movement of the solenoid 50. This solenoid will remain energized as long as current flows through these carbon electrodes 2! and 28. The sensitive current relay 3| will very accurately maintain at a constant value the current flowing through the arc through operation of the motor 45 in a forward or reverse direction as the case may be. This current will remain constant regardless of voltage changes of the power source 28, and regardless of the impurities bound to be included in the carbon electrodes Z'I and 28 which cause these carbons to have hard spots or soft spots as the case may be. Since the initial arc current is accurately controlled with respect to the initial voltage conditions of the system and actually standardized by means of the tap changing switches 33 and 3d the same Kelvin temperature of the arc can be obtained for all conditions, and hence a constant source of illumination, which will greatly improve conditions. in the graphic arts industry, is provided.

The arrangement for supporting the upper electrode 27 described thus far limits the amount of the electrode which can be consumed, and in Figs. 10 and 11 of the drawings there is illustrated a modification of the supporting means for the carbon electrodes whereby a substantially greater use of the carbons is possible. As illustrated in Fig. 10, there is provided an upper casting Ifiii which corresponds to the casting I36 of Fig. 3 of the drawings. One end of this casting is suitably secured to the upper movable carriage 93. The end of this casting not fastened to the movable carriage 93 is provided with a rectangular opening IBI arranged in a vertical position to receive therein for sliding reciprocating movement with respect thereto a carbon guide plunger I63 of rectangular cross section. The opening I6! is of sufiicient length and by virtue of its rectangular cross section will limit movement of the lift member I63 to movement only in the direction of its longitudinal axis. The upper end of the lift rod IE3 is connected by a suitable link I64 with one end of a lever I 65 pivotally mounted as indicated at I56 to the casting I611. The other end of the lever IE is pivotally connected-by means of. the

12 link I50 to the solenoid armature 5|. It will be apparent that energization of the solenoid 50 will cause vertical movement of the lift rod M3.

The lower end of the lift rod I53 disposed beneath the opening IiiI in the casting I653 is fastened by suitable stud bolts It? or the like, to a carbon clamp member I79, which is provided with a V-shaped notch IIiia for receiving therein the upper carbon electrode 2i. A suitable clamping plate I I I, maintained in clamping position by the clamping screw I72, holds the electrode 27 in the notch I'Iila. The clamping screw I 72 is illustrated as having an enlarged head ilia with suitable openings iIZb therein for manipulation by a clamp wrench, not shown. The carbon clamp I!!! is insulated from the lift rod M3 by mica insulating plates I'IE and Ill} and mice. sleeves Ill. As is best shown in Fig. 11 of the drawings, the conductor 25a may then be connected to the carbon clamp I It by a suitable terminal screw I'I9.

As illustrated in Fig. 10, the lower carbon 28 is supported by a lower carbon clamp Hi5 identical in every respect with the upper carbon clamp just described, thus making for ready interchangeability of parts. This lower carbon clamp I'iil is supported from a lower casting E89 which in turn is supported from the lower carbon carriage en. The lower carbon clamp Iii) is similarly insulated from the casting use by the mica insulators H5 and I I5 and the sleeve insulators Ill so that electrical connection with the conductor 2% through a terminal connection H9 may readily be made.

From the above description it will be apparent that the upper and lower carbons 21 and 28 may be utilized to substantially their entire extent with only the small portions retained within the clamps I'IO not being useable. In addition, the arrangement permits of electrical connections being made directly to the clamps I I6.

While there have been illustrated and described several embodiments of the present invention, it is not desired that the invention be limited to the constructions shown and described, for it will, of course, be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In an arc lamp comprising a pair of electrodes between which an arc is adapted to be drawn, the combination of a pair of electrode carriages each capable of supporting one of said electrodes, an electric motor for moving said carriages simultaneously in opposite directions to control the arc space between said electrodes, a power circuit connected to said electrodes, an electromagnet for moving one of said electrodes relative to the other, a relay including a winding connected in series with said power circuit, means responsive to operation of said relay for ener gizing said electromagnet to move said one electrode, and are current responsive means for controlling the energization of said electric motor to cause simultaneous movement of said electrodes in a manner to tend to maintain constant the arc current flowing between said electrodes.

2. In an arc lamp comprising a pair of electrodes between which an arc is adapted to be drawn, the combination of a pair of electrode carriages each capable of supporting one of said electrodes, a first motive means for moving said carriages simultaneously in opposite directions to maintain a predetermined arc space between said electrodes, 21 power circuit connected to said electrodes, second motive means comprising an electromagnet for moving one of said electrodes relative to the other, a relay including a winding connected in series with said power circuit, means responsive to operation of said relay for actuating said second motive means to move said one electrode, and are current responsive means for controlling said first motive means to cause simultaneous movement of said electrodes in a manner to tend to maintain constant the arc current iiowing between said electrodes.

In an arc lamp comprising a pair of electrodes between which an arc is adapted to be drawn, the combination of a pair of electrode carriages each capable of supporting one of said g electrodes, a first motive means for moving said carriages simultaneously in opposite directions to maintain a predetermined arc space between said electrodes, a power circuit connected to said electrodes, second motive means for moving one of said electrodes relative to the other, a first relay and a second relay each including a winding connected in series with said power circuit, means responsive to operation of said first relay for actuating said second motive means to move said one electrode, and means responsive to operation of said second relay for controlling said first motive means to cause simultaneous movement of said electrodes in a manner to maintain constant the arc current flowing between said electrodes.

4. In an arc lamp, the combination of a frame, upper and lower carbon carriages mounted for relative movement on said frame, means for supporting a carbon from each of said carriages in colinear relationship, a first rack connected to said upper CZLIJOD. carriage, a second rack connected to said lower carbon carriage, the longitudinal axes of said racks being disposed in spaced parallel relationship, a gear for engaging both of said racks to cause simultaneous movement of said racks in opposite directions, motive means connected to said gear, and means responsive solely to current flowing through said carbons for controlling said motive means to maintain a predetermined arc space between said carbons.

5. In an arc lamp, the combination of a pivotally supported frame, upper and lower carbon carriages mounted for relative movement on said frame, means for supporting a carbon from each of said carriages in colinear relationship, a first rack connected to said upper carbon carriage, a second rack connected to said lower carbon carriage, the longitudinal axes of said racks being disposed in spaced parallel relationship, a gear for engaging both oi said racks to cause simultaneous movement of said racks in opposite directions, electric motor means drivingly connected to said gear, means for controlling said carriages each capable of supporting one of said electrodes, a first motive means for moving said carriages simultaneously in opposite directions to maintain a predetermined arc space between said electrodes, a power circuit connected to said electrodes, second motive means comprising an electrcmagnet for moving one of said electrodes relative to the other, a first relay and a second relay each including awinding connected in series with each other and in series with said power circuit, means responsive to operation of said first relay for actuating said second motive means to move said one electrode, and means responsive to operation of said second relay for controlling said first motive means to cause simultaneous movement of said electrodes in a manner to maintain constant the arc current flovving between said electrodes.

7. In an arc lamp comprising a pair of electrodes between which an arc is adapted to be drawn, the combination of a pair of electrode carriages each capable of supporting one of said electrodes, an electric motor for moving said carriages simultaneously in opposite directions to maintain a predetermined arc space between said electrodes, a power circuit connected to said electrodes, an electromagnet for moving one of said electrodes relative to the other, a first relay and a second relay each including a winding connected in series with each other and in series with said power circuit, means responsive to operation of said first relay for energizing said electromagnet to move said one electrode, and means responsive to operation of said second relay for controlling the energization of said electric motor to cause simultaneous movement of said electrodes in a manner to maintain constant the arc current flowing between said elec trodes,

8. In an arc lamp, the combination of a supporting frame, a, pair of tubular members mounted on said frame with their longitudinal axes disposed in spaced parallel relationship, a pair of racks one disposed within each of said tubular members and each movable along one of said axes, a gear disposed between said tubular members at an intermediate position with respect thereto and drivingly engaged with each of said racks whereby rotation of said gear causes simultaneous movement of said racks in opposite directions, means defining a longtiudinally extending groove in adjacent faces of each of said members at both ends thereof, a first movable carriage extending into the grooves at one end of each of said members, means for fastening said first carriage to one end of one of said racks within the corresponding one of said members. a second movable carriage extending into the grooves at the other end of each of said members, means for fastening said second carriage to the other end of the other of said racks disposed within the other of said members, and longitudinally extending grooves defined in the ends of said racks to which no carriage is attached. for receiving therein a portion of the carrage adjacent that end of the rack when said carriages are moved a predetermined distance towards each other.

9. In an arc lamp, the combination of a supporting frame, a pair of tubular members of rectangular cross section mounted on said frame with their longitudinal axes disposed in spaced parallel relationship, a pair of racks one dis posed within each of said tubular members and each movable along one of said axes, a gear disposed betweensaid. tubular members at an intermediate position with respect thereto and drivingly engaged with each of said racks whereby rotation of said gear causes simultaneous movement of said racks in opposite directions, means defining a longitudinally extending groove in adjacent faces of each of said members at both ends thereof, a first movable carriage extending into the grooves at one end of each of said members, means for fastening said first carriage to one end of one of said racks withinthe corresponding one of said members, a second movable carriage extending into the grooves at the other end of each of said members, means for fastening said second carriage to the other end of the other of said racks disposed within the other of said members, and longitudinally extending grooves defined in each of the ends of said racks to which no carriage is attached for receiving therein a portion of the carriage attached to the corresponding end of the other of said racks when said carriages are moved a predetermined distance towards each other.

10. In an arc lamp, the combination of a supporting frame comprising a pair of angle memhers and cross members united to form a ladder like frame, a pair of tubular members mounted on said frame with their longitudinal axes disposed in spaced parallel relationship, a pair of racks one disposed within each ofsaid tubular members and each movable along one of said axes, a gear disposed between said tubular members at an intermediate position with respect thereto and drivingly engaged with each of said racks whereby rotation of said gear causes simultaneous movement of said racks in opposite directions, means defining a longitudinally extending groove in adjacent faces of each of said members at both ends thereof, a first movable carriage extending into the grooves at one end of each of said. members, means for fastening said first carriage to one end of one of said racks within the corresponding one of said members, a second movable carriage extending into the grooves at the other end of each of said members, means for fastening said second carriage to the other end of the other of said racks disposed within the other of said members, means for supporting in coaxial relationship a pair of carbon electrodes one mounted on each of said carriages, and means for automatically rotating said gear in a manner to produce constant illumination of an arc drawn between said carbon electrodes.

11. In an arc lamp, the combination of a, supporting frame, a pair of tubular members mounted on said frame with their longitudinal axes disposed in spaced parallel relationship, a pair of racks one disposed within each of said tubular'members and each movable along one of said axes, a gear disposed between said tubular members at an intermediate position with respect thereto and drivingly engaged with eachof said racks whereby rotation of said gear causes simultaneous movement of said racks in opposite directions, means defining a longitudinally extending groove in adjacent faces of each said members at both ends thereof, a first movable carriage extending into the grooves at one end of each of said members, means for fastening said first carriage to one end of one of said racks within the corresponding one of said members, a second movable carriage extending into the grooves at the other end of each of said members, means for fastening said second carriage to the other end of the other of said racks disposed within the other of said members, a reversible electric motor drivingly connected to said gear, manual means also connected to said gear, and a friction clutch for permitting actuation of said manual means without interference from said electric motor.

12. In an arc lamp, the combination of a pair of movable electrode carriages for supporting a pair of electrodes movable towards and away from each other along a line comprising the longitudinal axes of said electrodes, means for supporting said carriages for simultaneous movement in opposite directions, a source of potential which may vary in voltage within predetermined limits, an electric circuit connecting said source with said electrodes including a transformer, means for adjusting the potential output of said transformer to a predetermined value regardless of the potential of said source, motive means for moving said electrodes, and control means responsive solely to the current flow through said electrodes for controlling said motive means for maintaining constant the current flow through said electrodes.

13. In an arc lamp, the combination of a pair of movable electrode carriages for supporting a pair of electrodes movable towards and away from each other along a line comprising the longitudinal axes of said electrodes, means for supporting said carriages for simultaneous movement in opposite directions, a source of potential which may vary in voltage within predetermined limits, an electric circuit connecting said source with said electrodes including a transformer having primary and secondary windings, a plurality of taps on said primary winding for adjusting the voltage across said secondary winding to a predetermined value regardless of the potential of said source, motive means for moving said electrodes, and control means responsive solely to the current flow through said electrodes for controlling said motive means for maintaining constant the current flow through said electrodes.

14. In an arc lamp, the combination of a frame, upper and lower carbon carriages mounted for relative movement on said frame, means for fixedly supporting a lower carbon electrode from said lower carriage, a lever pivotally supported from said upper carriage, means for supporting an upper carbon electrode from said upper carriage to permit limited relative movement with respect to said carriage, the longitudinal axes of said electrodes being colinear and movement of said electrodes being limited solely to movement along said colinear axes, means for connecting one end of said lever to said last mentioned means, and motive means connected to the other end of said lever.

15. In an arc lamp, the combination of a frame, upper and lower carbon carriages mounted for relative movement on said frame, means for fixedly supporting a lower carbon electrode from said lower carriage, a lever pivotally supported from said upper carriage, means for supporting an upper carbon electrode from said upper carriage to permit limited relative movement with respect to said carriage, the longitudinal axes of said electrodes being colinear and movement of said electrodes being limited solely to movement along said colinear axes, means for connecting one end of I said lever to said last mentioned means, and an electromagnet having its armature connected to the other end of said lever to cause movement of said upper electrode in a direction away from said lower electrode.

16. In an arc lamp, the combination of a frame. upper and lower carbon carriages mounted for relative movement on said frame, means for fixedly supporting a lower carbon electrode from said lower carriage comprising a lower carbon clamp, a lever pivotally supported from said upper carriage, means for supporting an upper carbon electrode from said upper carriage to permit limited relative movement with respect to said carriage includin an upper carbon clamp identical with said lower carbon clamp, the longitudinal axes of said electrodes being colinear and movement of said electrodes being limited solely to movement along said colinear axes, means for connecting one end of said lever to said last mentioned means, an electromagnet having its armature connected to said lever to move said upper carbon away from said lower carbon to draw an arc therebetween, and means responsive to the current flow through said electrodes for energizing said electromagnet.

17. In an arc lamp, the combination of a frame, upper and lower carbon carriages mounted for relative movement on said frame, means for sup porting a carbon from each of said carriages in colinear relationship, a first rack connected to said upper carbon carriage, a second rack connected to said lower carbon carriage, the longitudinal axes of said racks being disposed in spaced REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 404,244 Atwood May 28, 1889 554,542 Seaverns Feb. 11, 1896 581,997 Okun May 4, 1897 632,707 Foote Sept. 12, 1899 645,784 Bornen Mar. 20, 1900 1,271,475 Kiefer July 2, 1918 1,904,541 Saurwein Apr. 18, 1933 1,915,981 Davis June 27, 1933 1,930,290 Streson Oct. 10, 1933 1,995,502 Elderkin Mar. 26, 1935 2,160,490 Strong Ma 30, 1939 2,468,570 Nyburg Apr. 26, 1949 

